Carbazole-Dendrimer-Based Donor−π–Acceptor Type Organic Dyes for Dye-Sensitized Solar Cells: Effect of the Size of the Carbazole Dendritic Donor

Abstract

A series of novel D-π-A type organic dyes, namely, GnTA (n = 1-4), containing carbazole dendrons up to fourth generation as a donor, bithiophene as π-linkage, and cyanoacrylic acid as acceptor were synthesized and characterized for applications in dye-sensitized solar cells (DSSCs). The photophysical, thermal, electrochemical, and photovoltaic properties of the new dyes as dye sensitizers were investigated, and the effects of the carbazole dendritic donors on these properties were evaluated. Results demonstrated that increasing the size or generation of the carbazole dendritic donor of the dye molecules enhances their total light absorption abilities and unluckily reduces the amount of dye uptake per unit TiO2 area because of their high molecular volumes. The latter was found to have a strong effect on the power conversion efficiency of DSSCs. Importantly, electrochemical impedance spectroscopy (EIS) revealed that the size or generation of the donor had a significant influence on a charge-transfer resistance for electron recombination at the TiO2/electrolyte interface, causing a difference in open circuit voltage (Voc) of the solar cells. Among them, dye G1TA containing first generation dendron as a donor (having lowest molecular volume) exhibited the highest power conversion efficiency of 5.16% (Jsc = 9.89 mA cm(-2), Voc = 0.72 V, ff = 0.73) under simulated AM 1.5 irradiation (100 mW cm(-2)).

Synthesis and photochemical properties of 3,6-di-tert-butyl-9H-carbazole derivatives

“…Thus, carbazole derivatives are used as synthons for preparation of luminophores [7], and branched 3,6disubstituted derivatives of carbazole are applied as building blocks for creation of more complex organic molecules [8]. Compounds of this type are now used for the synthesis of OLEDs because of their high hole conductivity, photochemical stability, and electroconductivity [9][10][11]. The carbazole-based dendrites are shown to act as luminescent gelators for ordered organogels [16,17].…”

D–π–A organic dyes with various bulky amine-typed donor moieties for dye-sensitized solar cells employing the cobalt electrolyte

“…Also, the molar absorption coefficient (e) of the SGT-102 dye was higher than SGT-101 dye due to p-extended conjugation. Unlike expectation, the SGT-103 dye containing the bulky phenothiazine donor group showed a maximum absorption of 484 nm, which was red-shifted by 5 nm, compared to the other dyes, since it has been recently reported that the blue-shifts in solution with the number of the donor groups in the starburst 2D-p-A organic dye would be expected due to the higher ICT energy levels resulting from the increase of donor moieties [20,21]. However, increasing the number of the donor moiety improves the molar extinction coefficients of the ICT absorption peaks of the dyes.…”

Benzimidazole‐indole‐chalcone connected methacrylate‐based side chain D‐π‐A polymer and its application in organic photovoltaics

“…Specifically, their applications in polymer solar cells (PSCs), polymer light‐emitting diodes (PLEDs), and organic field‐effect transistors (OFETs) offer opportunities for a renewable energy supply as well as the development of display and information technologies . To achieve high‐performance organic sensitizers, many studies have focused on improving the following key properties: (i) improving the light harvesting ability and efficiency, (ii) molecular energy level, and (iii) decreasing the charge recombination reactions at the FTO/TiO 2 /polymer/electrolyte interface . In view of the polymer development, these have been mainly done by engineering their molecular structure and at either donor or acceptor moieties.…”